package com.wushijia.sort;

import java.util.Arrays;

/**
 * 归并排序
 *
 * @author Administrator
 * @date 2021-06-16 9:45
 */
public class MergeSort {

  public static void main(String[] args) {
    int[] arr = {4, 1, 6, 9, 10, 22, 1, 7, 8, 100};

    sort(arr);

    System.out.println(Arrays.toString(arr));

  }

  private static void sort(int[] arr) {
    int[] temp = new int[arr.length];

    sort(arr, 0, arr.length - 1, temp);
  }

  private static void sort(int[] arr, int left, int right, int[] temp) {
    if (left < right) {
      int mid = (left + right) / 2;
      sort(arr, left, mid, temp);
      sort(arr, mid + 1, right, temp);
      merge(arr, left, mid, right, temp);
    }
  }

  private static void merge(int[] arr, int left, int mid, int right, int[] temp) {
    int i = left;
    int j = mid + 1;
    int t = 0;

    while (i <= mid && j <= right) {
      if (arr[i] <= arr[j]) {
        temp[t++] = arr[i++];
      } else {
        temp[t++] = arr[j++];
      }
    }

    while (i <= mid) {
      temp[t++] = arr[i++];
    }

    while (j <= right) {
      temp[t++] = arr[j++];
    }

    t = 0;

    while (left <= right) {
      arr[left++] = temp[t++];
    }
  }
}
